Stock feeder for printing press

ABSTRACT

A stock feeder for an offset printing press has vacuum suckers arranged below a stack of stock, like envelopes, with the suckers being swung curvilinearly into and out of engagement with the lowermost envelope in the stack in order to feed it from the stack into the press. The suckers have an initial twisting motion after they grip the lowermost envelope before lowering it from the stack, and thereby separating it from the stack without disturbing the next uppermost envelope. As the edge only of the envelope is twisted downward and yet does not lower the body of the envelope, two purposes are accomplished. First, the vacuum between the first and second sheet is broken and second, the edge of the envelope has been released from resting on the inwardly turned leaf springs. As the suckers start their downward motion, a pressure roll swings toward the envelope and contacts the envelope on the upper side when the suckers have moved downward about three-fourths of their travel and at which point the suction or vacuum from the vacuum pump of the press is released. The pressure roller then continues rearward toward the rubber feed roll until it clamps the envelope against the feed roll so as to positively advance it into a set of pull-out rolls and thence into the press.

United States Patent [1 1 Thomsen STOCK FEEDER FOR PRINTING PRESS ElmerR. Thomsen, 1021 NE. 135th Ave., Portland, Oreg. 97230 [22] Filed: July20, I973 [21] Appl. No.: 381,352

[76] Inventor:

'rimary Examiner-Richard A. Schacher ssistant Examiner-Bruce H. Stoner,Jr. ttorney, Agent, or Firm-Edward F. Connors 14 1 July 8,1975

[57] ABSTRACT A stock feeder for an offset printing press has vacuumsuckers arranged below a stack of stock, like envelopes, with thesuckers being swung curvilinearly into and out of engagement with thelowermost envelope in the stack in order to feed it from the stack intothe press. The suckers have an initial twisting motion after they gripthe lowermost envelope before lowering it from the stack, and therebyseparating it from the stack without disturbing the next uppermostenvelope. As the edge only of the envelope is twisted downward and yetdoes not lower the body of the envelope, two purposes are accomplished.First, the vacuum between the first and second sheet is broken andsecond, the edge of the envelope has been released from resting on theinwardly turned leaf springs. As the suckers start their downwardmotion, a pressure roll swings toward the envelope and contacts theenvelope on the upper side when the suckers have moved downward aboutthree-fourths of their travel and at which point the suction or vacuumfrom the vacuum pump of the press is released. The pressure roller thencontinues rearward toward the rubber feed roll until it clamps theenvelope against the feed roll so as to positively advance it into a setof pull-out rolls and thence into the press.

8 Claims, 12 Drawing Figures 1 STOCK FEEDER FOR PRINTING PRESSBACKGROUND OF THE INVENTION 1. Field of the Invention The presentinvention generally appertains to improvements in apparatus for removingflexible sheets in consecutive order from a stack and especially to newand novel improvements in apparatus for feeding individual sheets fromthe bottom of a stack of such sheets to a sheet handling machine.

The present invention relates to new and novel improvements in feedersfor feeding stock to an offset printing press or letter press.

2. State of the Prior Art Since the feeder of the present invention hasbeen developed for use with printing presses for feeding stock, likeenvelopes, to the press such environment will be retained in relation tothe description of the background of the feeder.

In normal operation in feeding stock in the Multilith press, the stockis placed in the feeder at the rear end of the press. The top sheet isthen lifted by suckers or vacuum cups and brought forward into feedrolls and then fed to the printing cylinder by tapes. It is obvious thatthe primary drawback of such feeding arrangement is that it is necessaryto stop the press in order to replenish the stock, which is placed inthe stock hopper of the feeder from the top.

In view of this drawback, there have been many attempts to feed thestock from the bottom of the stack by engaging the lowermost sheet inthe stack with a suction means and gripping the sheet to pull itdownwardly away from the stack.

One example of an apparatus for feeding individual sheets from thebottom of a stack of such sheets to a sheet handling machine is shown inU.S. Pat. No. 3,093,371, issued June 11, 1963. In such patent, a suctionmeans is disposed beneath the stack of sheets and is swung curvilinearlyinto and out of engagement with the lowermost sheet in the stack. In itsinitial engagement with the lowermost sheet, the suction means graspsthe sheet and draws the latter straight downwardly as the suction meanscommences its downward swinging movement away from the stack. A rodarrangement cooperates with the suction means to move in and out ofsupporting relation with the stack in consort with the engagement of thelowermost sheet in the stack by the suction means. And in such manner,an attempt is made to prevent the next uppermost sheet in the stack frombeing pulled downwardly by the suction means as it moves the lowermostsheet down away from the stack.

In U.S. Pat. No. 3,172,655, issued Mar. 9, 1965, a suction nozzle ismounted for swinging movement on a horizontally transverse axis below astack of sheets and is moved upwardly to grip the lowermost sheet.Cooperating with the suction nozzle in its downward swinging movementaway from the stack is a blank separator having a laterally projectingtongue provided with an opening for discharging an air jet. When thesuction nozzle moves downwardly carrying the engaged marginal edgeportion of the lowermost sheet away from the stack, the tongue movesinwardly between the engaged sheet and the next uppermost sheet anddischarges an air jet between the sheet so as to prevent the nextuppermost sheet from being pulled downwardly by the suction nozzle.

In U.S. Pat. No. 3,071,369, issued Jan. 1, 1963, a suction cup isdisposed below a stack of flexible sheets and is actuated by a cam meansso as to be moved in a substantially direct up and down movement towardand away from the stack. In such patent, there is a rapid initialretracting movement of the suction cup due to a bellows arrangement incooperation with the cam means. Such is intended to effect a quickjerking downward movement of the suction cup and thereby realize anefficient removal of only one sheet from the stack.

In U.S. Pat. No. 3,658,319, issued Apr. 25, 1972, an arrangement ofrocking side suckers and a central sucker is provided wherein thecentral sucker operates to engage the lowermost sheet while, at the sametime, a blower nozzle forces air between the gripped sheet and the nextuppermost sheet to assist in forming a gap between the engaged sheet andthe next sheet thereabove. A separator tongue then is swung into the gapbetween the engaged sheet and the next sheet thereabove and the sidesuckers operate with a time delay relative to the start of suction ofthe central sucker and engage the engaged sheet to complete the downwardpulling movement of the sheet away from the stack.

In the various feeders, as disclosed in the above patents which areexemplary of the prior art, the sheet that is engaged by the suctionmeans is pulled directly downwardly as the suction means swings awayfrom the stack or moves downwardly from the stack. Whether the suctionmeans swings curvilinearly or moves in a substantially rectilinear pathbeneath the stack and regardless of any mechanical means provided tooperate in sonsort with the downwardly moving suction means. there isstill no reliable arrangement provided whereby it can be assured thatonly one sheet will be removed at a time. In all such patented devices,there exists the possibility of two sheets being removed from the stackat the same time. This is true even where there are attempts to providemechanical separators between the engaged sheet and the next sheet or toprovide air means for blowing between the sheets so as to separate thesheet engaged by the suction means and the next sheet thereabove in thestack.

None of the known bottom feeders operate with such degree of reliabilitythat the possibility of double feeding is obviated. And yet, thismalfunctioning is the most troublesome one, especially in feeding stockto a printing press.

SUMMARY OF THE INVENTION An important feature of the present inventionresides in the provision of a unique system of suckers in a sheet feedermechanism whereby the removal of one sheet at a time is positivelyensured. Thus, it is a primary object of the present invention toprovide a very novel and unique method and apparatus of sheet separationin a feeder. In accordance with the present invention, the suckerscontact the lowermost sheet in a stack, but before they start a downwardmotion in gripping the sheet andpulling the sheet away from the stack,the gripped edge of the sheet is twisted downward while at the sametime, because of the twisting action, it is pulled off leaf springs orthe like which support or carry the leading edge of the pile or stack.

It has been found in prior practice, regardless of various mechanicalarrangements such as disclosed in the aforesaid patents, that doublesheet feeding does occur. This is especially true in feeding heavystock, such as card stock, wherein the cards lie close together and asthe first card is pulled away it also pulls the second card downwardlybecause of the vacuum action between the first and second cards. Suchdougle sheet feeding is overcome by the present invention wherein thesuckers in contacting the lowermost sheet have a revolving motion beforelowering. Because of such revolving mo tion, the suckers twist the edgeof the sheet and thereby separate the edge of the engaged sheet from thenext sheet thereabove.

Because the sheet is merely twisted and then pulled downward off theleaf spring carriers, heavy material such as card stock, booklets, etc.can be fed.

If the stock had to be moved rearward and off a solid ledge, a buckle inthe sheet would have to occur. Stiff and heavy material could not thenbe fed. In this invention the sheet does not buckle and therefore veryheavy material can be fed.

The suckers are in the form of suction cups provided on a hollowmanifold rod arranged transversely of the stack and rotatably journaledat its ends in a pair of supporting arms, which are pivoted on aparallel shaft that has one of its outer ends provided with a bell crankhaving a cam roller which is engaged by a cam on a reciprocating slide.The sucker manifold is retained in a raised position by spring means andis moved downwardly, against the urgement of the spring means, by thepositive action of the cam in engaging the roller and rotating the crankto cause the arms to swing downwardly away from the stack. Prior to thedownward movement of the arms, the manifold rod is rotated. Thus, as thesuction cups contact the sheet, just before they start the downwardmotion under the impetus of the supporting arms, the initial downwardmovement of the arms is reacted to and resisted by the restraining leverto cause the manifold to commence a rotary counter-clockwise motion. Themanifold is moved rearward while in its rotating action to prevent thesheet from being pulled forward. If the manifold merely rotated on itsjournals without moving rearward, the sheet would then be pulled forwardbecause the suckers would be compelled to move forward. Because of themotion of the manifold, the axis or joint of pivot is actually center ofthe top of the suckers. Such rotary motion will cause the suction cupsengaging the leading edge of the engaged sheet to twist sudh edgedownwardly away from the next sheet thereabove.

The manifold or suction rod is connected by a flexible tube to theconventional vacuum tube of the printing press which has a valve meansthat controls the timing of the supply of vacuum to the manifold rod.Such a press is well-known in the art; for example, the A. B. Dickoffset press manufactured by the A. B. Dick Co. of Chicago, Illinois andthe Chief l5 and Itek presses manufactured by American Type Founders ofLouisville, Kentucky.

The operation of the suckers is timed so that the vacuum sucks the sheetat the high point of the suckers in relation to the stack and isreleased just before the suckers are at the low point in regard to theirdownward movement below the stack of sheets.

The cam carrying slide is mounted on the feeder frame alongside thestock hopper for forward and rearward sliding movement under the controlof a feeder linkage from the printing press. Such slide also carriesanother cam which is adapted to engage a roller provided on the end of abell crank for a pressure roll which operates in coordinated relationwith the suckers and in cooperation with a feed roll. The feed roll isrotated through a gearing in relation with the operating mechanism ofthe press so that it is rotated in time relation therewith with thenormal pull-out rolls of the feeder.

The pressure roll is retained in a normally inoperative position out ofengagement with the sheet and away from its relation with the feed rollby means of a cam which compels the pressure roll forward and away fromthe feed roll. The pressure roll is returned to the feed roll by meansof a spring. As the cam moves forward, the roller of the bell crankdrops off the cam and permits the pressure roller to move rearward byspring action to contact the feed roll.

When the slide is in its rearward position, the sucker rod will rise andthe suckers will contact the lowermost sheet with the bell crank beingin high position. With the suckers at the high point, they are incontact with the lowermost sheet. At this point, the vacuum is engagedin the valve of the press and the slide is in its most rearwardposition. As the slide is pulled forward by the lever actuatingmechanism from the press, the suckers carrying the sheet are pulleddownward toward the rubber feed roller. Before the suckers movedownwardly, they are rotated counter-clockwise so as to twist the edgeof the engaged sheet away from the stack and thereby break the suctionbetween the engaged sheet and the next uppermost sheet. The suckers havea revolving motion before lowering so as to separate the edge of theengaged sheet from the next above sheet. Since the sheets are separatedat the edge, the vacuum which normally exists between the superimposedsheet is broken and atmospheric air enters between the sheets.

As the suckers carrying the sheet are pulled downwardly by the action ofthe arms being swung by the cam rod which is rotated under the positiveaction of the engaged bell crank that is being swung downwardly by theforwardly reciprocating cam slide, the engaged sheet is moved downtoward the feed roll. Before the sheet contacts the feed roll, thepressure roll is moved, under the spring urgement, into a position abovethe sheet and then, as the sheet contacts the feed roll, the pressureroll squeezes the sheet against the feed roll and causes the sheet to beimpelled towards the normal pull-out rolls. The suckers remain in a downposition because the cam slide is still in positive engagement with theroller on the bell crank and holds them down until the sheet hascleared.

When the sheet has traveled about seven inches, the pressure roll thenlifts off the sheet because the cam slide starts its rearward action andengages the roller on the bell crank of the pressure roll and cause thebell crank to be swung downwardly. At this same time, the roller on thebell crank for the suction rod is free to move upwardly under the springurgement into a notched-out portion in the cam slide provided in advanceof the cam segment thereon that is adapted to engage the bell crankroller. Thus, the suckers are swung upwardly to contact the next sheetto be engaged.

Such coordinated movements of the suckers and the pressure roll areeffected by the cam slide which has cam segments that engage the rollerson the bell cranks for each of the components, namely, the sucker rodand the pressure roll.

Another important object of the present invention is to provide meansfor retaining forward edge portions of the sheets in the stack as thelowermost sheet is being separated therefrom. Depending upon the natureof the sheet material, that is with respect to its weight, softness orevenness, various mechanical means may be provided and the provisionthereof constitutes another feature of the present invention.

Such means engages the leading edge of the stock being carried andcomprises the inwardly turned lower ends of leaf springs which arevertically mounted at the front of the stock hopper and have their lowerinwardly turned ends disposed in the open space at the bottom of thehopper through which open space the suckers are adapted to move inengaging the front edge portion of the sheets in the stack.

In another instance, needle screws are moved inwardly to contact theleading edge of the lowermost sheet in the stack and such is veryhelpful in running card stock especially.

In other instances, the springs may be used alone by backing out theneedle screw so that they do not contact the stock. And in othercircumstances, the springs may be put out of use by turning themoutwardly of the hopper so that they are not in vertical position tohave their lower ends engage the stock.

With some types of stock, both the springs and the needle screws may besimultaneously used.

Another important object of the present invention is to provide meansfor controlling the height of the suckers. The purpose of this is thatbecause of the type of stock, or paper or sheet material or thecondition thereof, it is desirable to lower or raise the suckers forbetter contact with the sheet.

To realize such adjustment, an offset rod is journalled between thewalls of the hopper rearwardly and below the pivoted ends of thesupporting arms for the sucker tube. Such offset rod has eccentric endsand the rod is pivoted to a threaded adjustment rod which is attached toa cross bar between the sides of the hopper frame at the rear thereof.By adjusting the threaded screw, the offset rod is rotated which will,due to its eccentric journalling, raise and lower it below the pivotedends of the arms. Such ends are pivoted to blocks fixed on the cam rodand the arms have cut-outs whereby they can be bodily moved on theirpivots relative to the anchoring blocks to which they are pivoted and bymeans of which they are attached to the actuating rod for effecting anupward and downward swinging movement of the sucker rod.

Another important object of the present invention is to provide meansfor delaying the rise of the suckers under the impetus of the cam slide.This is especially useful depending upon the length of the stock, as forexample in feeding long envelopes.

The rise of the suckers is delayed by effecting a delay in the rise inthe bell crank and this is carried out by means of a pair of cooperatinglevers which are adapted to be hooked together and which are underspring urgement in being retained in their hooked together relation butwhich can be spread apart as the cam slide moves forwardly. One of thelevers has a cam edge that is in advance of the cam segment that isprovided to contact the roller on the bell crank for the sucker rod and,therefore, the initial contact of such lever effects a delay in the realcontact of the cam slide with the roller on the bell crank, whereby therise of the sucker rod is delayed.

Another important object of the present invention is to provide asimple, compact and very practical feeder mechanism for feeding flexiblesheet material in a true one by one fashion regardless of the naturethereof and irrespective of the apparatus to which such material is fed.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. I is a side elevational view ofthe feeder of the present invention.

FIG. 2 is a top plan view thereof.

FIG. 3 is a longitudinal vertical sectional view taken substantially online 3-3 of FIG. 2 and showing the suckers their highest positions andin engagement with the lowermost sheet in the stack.

FIG. 4 is a view similar to FIG. 3 showing the suckers on their way downand the pressure roller in a position about to engage the pulled downsheet.

FIG. 5 is a view similar to FIGS. 3 and 4 but showing the suckers intheir lowermost position and showing the pressure roll engaged with thesheet and holding the sheet onto the feed roll with the sheet beingadvanced by the feed roll to the pull-out rolls that are driven by thepress.

FIG. 6 is a side elevational view, similar to FIG. 1, but showing thesuckers in a down position and the pressure roll engaging the sheet andholding the sheet on the feed roll.

FIG. 7 is an exploded perspective view of the suckers, the pressure rolland the adjustment rod for varying the effective height of the suckers.

FIG. 8 is a side elevational view, similar to FIGS. I and 6, and showingthe suckers beginning the downard stroke.

FIGS. 9, l0 and 11 are pictorial and somewhat diagrammatic views,showing the action of the suckers in effecting a rearward twist of theengaged sheet with the suckers effecting an initial rotating actionbefore they start their downward swinging movement away from the stackso as to realize the rearward twist of the sheet and, consequently, theeffective separation of the engaged sheet from the stack so as to breakthe vacuum existing between the engaged sheet and the next uppermostsheet in the stack.

FIG. 12 is a fragmentary perspective showing of the restraining leveragearrangement between the sucker rod which is rotatably journalled in theouter ends of the pivoted supporting and actuating arms and the frame ofthe feeder.

DESCRIPTION OF THE PREFERRED EMBODIMENT For exemplary purposes, thesheet feeder 10 is shown in the accompanying drawings in structural andoperational association with an offset printing press 12, such as one ofthe conventional presses described in the foregoing. Since such press isconventional and wellknown in the art, the press is only fragmentarilyshown in FIG. 2. The frame I4 of the feeder 10 is attached to the pressby having its side plates 16 and 18 mounted on the press frame in aposition, as shown in FIG. 6. For this purpose, the transversely spacedand parallel side plates 16 and 18 are provided with apertured mountingfeet 20 that are adapted to be anchored by bolts on the press frame.

The press 12 is provided with a feeder operating linkage 20a, as shownin FIG. 6, and such feeder linkage, which is standard equipment on thepress, is adapted to actuate the operating mechanism of the feeder 10,as will be described. The feeder I is positioned at the feed or frontend of the press and has its outlet end 22 disposed above theconventional feed tapes 24 of the press which tapes carrying the sheetsfed from the feeder under the conventional sheet riders and into theprinting cylinders of the press, as will be well appreciated by thoseskilled in the art.

The feeder is provided with a bottom plate 26 that is mounted betweenthe side plates and which provides the bottom of a supply hopper 28within which the sheets of stock, such as the illustrated envelopes 30,are disposed. The envelopes are piled in a stack within the hopper andare fed from underneath the pile or stack in one by one consecutivefashion. The hopper is composed of a front plate 32 and a complementaryupstanding rear plate 34. The rear plate 34 is adjustable forwardly andrearwardly between the side plates and by mounting adjustment means onthe bottom plate 26.

The hopper further includes side plates 36 which are positioned betweenthe front and back plates 32 and 34, respectively, and which can bemoved apart or to gether so as to accommodate stock of various widths.As shown in FIG. 2, the hopper side plates 36 are slidably mounted in aslot 38 in the bottom plate 26 between the frame plates 16 and 18 byvirtue of slide blocks 40 that carry thumb screws 42 for locking theplates in set positions along the extent of the cross-bar 38.

As shown in FIGS. 3-5, the bottom plate 26 of the hopper 28 terminatesrearwardly of the front plate 32 so that a feeding space 44 is provided.The front terminating edge 46 of the bottom plate is inclined downwardlyto provide a pull-off surface for the envelopes to slide on as they arebeing pulled downwardly from the stack.

A sucker rod 48, which is in the form of a hollow manifold. is providedwith suckers 50, which are in the form of vacuum cups, and which arespaced along the extent of the sucker rod that is adapted to beoperatively movable within the feeding space 44. The sucker rod isconnected by a flexible tube 52 to the normal vacuum system of theprinting press 12, which, as will be understood by those skilled in theart, has a valve means that is operated in time relation with themovements of the sucker rod in relation to the stack of envelopes.

As shown more particularly in FIG. 7 the sucker rod 48 has its endportions 54 rotatably journaled in the forward ends 56 of operating arms58 which support the sucker rod and which move the same in a curvilinearpath of movement relative to the overhead stack of envelopes. The arms58 are provided with enlarged rear mounting ends 60 that are pivoted bypivot pins 62 in clevises 64 which integrally depend from blocks 66. Theblocks 66 are sleeved onto an actuating rod 68 and are held in fixedpositions by set screws 70.

The actuating rod 68 is provided at one end with a bell crank 72 thathas a cam roller 74 provided thereon. The bell crank 72 with the camroller 74 is disposed ex teriorly of the side plate 18 and is adapted tobe engaged by a cam segment 76 provided on a slide plate 78 that isslidably mounted on the outer face of the frame side plate 18 forreciprocating backward and forward movement under the actuation of thepress linkage 20a, as shown in FIG. 6, for example.

The end portion 54a of the sucker rod projects beyond the adjacentmounting and supporting arm 58 and is fixed to a link 780 by a pin 79.The link 78a is pivoted to a link 80, as shown in FIGS. 7 and I2. Thelink 80 is attached by a pivot pin 82 to an anchoring sleeve 84 which isfixed to the frame side plate 18 and projects inwardly therefrom. Thelinks 780 and 80 constitute a restraining linkage which secures thesucker rod 48 to the frame in a manner so as to effect the initialrearward revolving or rotating motion of the sucker rod before thesucker rod is moved downwardly under the actuation of the arms 58 in themanner as shown in FIGS. 3-5.

The downward swinging movement of the sucker rod is controlled by thearms 58 under the action of the bell crank 72 and the cam segment 76 ofthe slide plate 78. The operating and supporting arms 58 for the suckerrod are also provided with spring biasing means which is in the form ofcoil springs 86 that are anchored to depending lugs 88 on the rear endportion 60 of each of the arms 58 and to a cross bar 880 on the frame.

The end of coil springs 86a are fixed to depending pins 90 on a crossrod 92 and to the frame bar 880. The rod 92 is rotatably journaledtransversely between the side plates 16 and 18 of the feeder frame andswingably supports a pressure roll 94. The pressure roll 94 is providedat its ends with mounting sleeves 96 that receive threaded adjustmentrods 98 which are positioned through vertical openings in the rod 92 andare held in adjusted fixed positions thereby by locking nuts 99. In thisfashion, the height of the pressure roll 94 can be adjusted. And moreparticularly, the position of the pressure roll in relation to a feedroll 100 can be controlled.

As shown in FIGS. 3-5, the feed roll 100, which is preferably formedfrom rubber, is rotatably journaled between the side plates 16 and 18 ofthe feeder frame 14 and is positioned below and slightly rearwardly ofthe feeding space 44 from the hopper 28. The pressure roll 94 is adaptedto cooperate therewith in holding a sheet thereagainst after the sheethas been lowered from the stack by the sucker rod 48. The feed roll isrotated in a counterclockwise direction by a gearing 102 which alsodrives a pair of pull-out rolls 104 in a counterclockwise direction andat the same rate of rotation as the feed roll 100, as shown in FIGS.3-5.

The pull-out rolls 104 are disposed in cooperating relation one abovethe other and are adapted to receive therebetween the pulled-off sheetwhich is given its initial forward impetus relative to the nip betweenthe pull-out rolls by the feed roll 100 with the pressure roll servingto hold the sheet onto the feed roll so that it is frictionally engagedwith and moved forward by the feed roll 100 as can be appreciated from aconsideration of FIG. 5.

The gear means 102 assures a proper rotation between the feed roll 100and the pull-out rolls 104 which advance the sheet to the tapes 24 ofthe printing press. The gearing I02 is driven by gearing from theprinting press so as to assure the proper rotary speed between thepull-out rolls and the sheet riders and printing cylinders of the presswith the sheets being fed onto the types and under the sheet riders andthen into the printing cylinders, as will be well understood by thoseskilled in the art.

The pressure roll 94 is swung into a sheet clamping relation with thefeed roll 100 by the action of the spring means 86a and is retained in aposition away from the feed roll, as shown in FIG. 3, by the action ofthe slide mechanism 78 which operates on a roller 106 that is providedon a bell crank 108 which is disposed exteriorly of the frame plate 18and which is connected by a pin 110 with one end of the pressure rollsupporting rod 92. The center gear in the gearing 102 between the gearsfor the pull-out rolls 104 and the feed roll 100 is rotatably journaledon one end of the rod 92 internally at the inner face of the frame plate16, as shown in FIGS. 2 and 7.

Depending upon the particular type of stock, such as the nature of thematerial, for example, the softness. unevenness, or the like, variousmethods are provided for sheet separation and for retention, in thisregard, of the forward edges of the lowermost envelope in the stack asthe pulled out envelope is being lowered from the stack by the suckers50.

As best shown in FIGS. 3-5, the leading edge of the bottom envelope 30bin the stack after the preceding envelope 30a has been pulled down fromthe stack by the suckers 50 is retained by various means. Thus, springbars 112, like flat clock springs, are vertically oriented on theoutside of the front wall 32 of the hopper means and are held invertical positions thereon by pins 114. The free lower end portionsproject downwardly below the end of the front wall and are inturnedtowards the stack so that the inturned end portions 116 can engage andretain the leading edge of the bottommost sheet 30b in the stack 30.

In some instances, additional retainers and separators will be desiredand, for this reason, needle screws 118 are adjustably supported inthreaded bores in a cross bar 120 fixed between the frame plates 16 and18 and are rotatable therein so that their needle points 122 can bepositioned beneath the leading edge of the bottom envelope 30b in thestack 30, as shown in FIGS. 3S.

The springs 112 and needle screws 118 may be conjointly employeddepending upon the nature of the stock. In such instance, the springswill be left in the vertical positions, as shown in FIGS. 3-5, and theneedle screws will be rotated until their inner pointed ends 122 justtouch the stock.

The spring bars 112 are disposed adjacent the ends of the front plateand they may be put out of use by swinging them upwardly and outwardlyso that they will not be in operative positions. Then, only the needlescrews 118 will be used.

Accordingly, it can be seen that there are three means of sheetseparation for supporting the leading edge of the bottom sheet of thestock. Such supporting means serves as means to help to separate thesheets since it works in conjunction with the suckers 50 to hold thenext succeeding sheet 30b in the stack as the bottommost sheet 30a isbeing pulled therefrom by the downwardly moving suckers 50.

Means is provided for adjusting the effective or working height of thesuckers 50. As shown in FIGS. 2, 3 and 7, an offset rod 124 is providedwith eccentric ends 126 which are rotatably journaled in the frame sideplates 16 and 18 with the offset rod underlying the rear end portions 60of the mounting arms. The end portions 60 are provided with slots 128that accommodate the sup porting blocks 66 with the end portions 60being free to be moved about the pivots 62 relative to the blocks 66 byvirtue of the slots 128. Such movement is effected by rotating theoffset rod 124. For this purpose, an adjustment rod 130 is pivotallyattached, as at 131, to the offset rod and the adjustment rod extendsrearwardly and is provided with a threaded end portion 132 that extendsthrough a bore 134 in a bar 136 which is fixed between the frame sideplates [6 and I8. A knurled knob 138 is threaded onto the end portion132 and bears against the cross bar 136. The adjustment rod 130 has afixed collar 140 against which one end of a coil spring 142 coiled aboutthe rod bears with the other end of the spring bearing against the crossbar 136. As can be appreciated, manual rotation of the knob 138 willcause the adjustment rod to be moved axially longitudinally of thefeeder frame and will result in an effective clockwise orcounterclockwise rotary movement of the offset rod I24. By virtue of theeccentric mounting of such offset rod 124, it will rise up against ormove down from the end portions 60 of the sucker rod supporting arms 58and cause the arms to be moved up or down in respect to their supportingblocks 66 on the supporting and operating rod 68. This will cause thesucker rod to be moved to higher or lower effective heights. Such actionwill be governed by the type of stock or the condition thereof, forexample. The necessity to lower or raise the suckers 50 is dictated bythe need for better contact thereof with the sheets of stock in thestack.

As shown in FIGS. 1, 6 and 8, the slide plate 78 is provided withlongitudinally extending slots 144 and 146 which form trackways thatslide on guide pins I48 and 150 that are fastened to the exterior of theside plate 18 of the feeder frame. The slide plate 78 is provided withthe cam segment 76 that engages the roller 74 of the crank lever 72 andwhich effects the downward swinging movement of the arms 58 thatproduces the downward swinging action of the sucker rod 48 that is shownin its downward movements in detail in FIGS. 3-5. The slide plate alsohas a cam member 152 that acts on the roller 106 for the bell crank 108of the pressure roll 94.

For a better understanding of the operation of the feeder, attention isfirst directed to FIGS. 1, 6 and 8 which show the sequence of events inrelation to the slide plate and the bell cranks 72 and 108 for thesucker rod 48 and for the pressure roll 94.

With reference to FIG. 8, it will be noted that the slide plate 78 isstarting forward and that the suckers 50 are in their upper position andare beginning the downward stroke with the cam segment 76 engaging theupper roller 74 and causing the crank lever 72 to be swung downwardly ina counterclockwise direction. Continuing to FIG. 6, it can be seen thatthe sucker rod 48 is in its down position and would be held in suchposition because the cam segment 76 is seated over the roller 74 on thebell crank 72 which would hold the sucker rod 48 in a down position. InFIG. 1, the sucker rod is shown in its uppermost position to which ithas been urged by the spring means 86 since the cam segment 76 has movedrearwardly to permit the crank lever 72 to ride up to its uppermostposition.

The cam segment 152 has an upwardly and rearwardly inclined rear edge154 and a straight bottom edge 156. The bottom edge acts on the roller106 to hold the pressure roll 94 in its inoperative position, as shownin FIG. 3. As the slide plate 78 moves forwardly the roller 106 isallowed to travel up the inclined cam face I54 and this permits thesprings 86a to be active to swing the pressure roll into engagement withthe feed roll 100, as shown in FIGS. 4 and 5.

When the slide plate 78 moves rearwardly the cam segment I52 will act onthe roller I06 to cause the pressure roll to be swung back to itsinoperative position, as shown in FIG. 3. And, as the slide plate 78moves rearwardly, the roller 74 for the bell crank 72 of the sucker rodactuating mechanism will be allowed to move upwardly under the action ofthe springs 86 and thus will allow the sucker rod 48 to move to itsuppermost position where the suckers 50 will engage the underside of thefront edge portion of the lowermost envelope in the stack, as shown inFIG. 3.

Thus, when the slide plate 78 is in its forward position toward thedelivery end of the feeder 10, the suckers 50 are down and the pressureroll 94 is against the rubber feed roll 100, as shown in FIG. 5. As theslide plate 78 is reciprocated rearwardly by the operating linkage afrom the printing press, the suckers 50 will rise and will contact theunderside of the lowermost envelope a in the stack, as shown in FIG. 3.With the suckers 50 in the high position, they contact the underside ofthe front edge portion of the envelope 30a. At this point, the vacuum isengaged in the printing press valve and the slide plate 78 is in itsmost rearward position.

As the slide plate is pulled forwardly on the guide pins I48 and 150 bythe press operating linkage 20a, the cam segment 76 will engage theroller 74 and, through the crank lever 72 and the rod 68 and the arms58, will start the suckers 50 in their down position. As the arms 58start downwardly to swing the sucker rod 48 in the downward curvilinearmovement, the initial downward swinging action of the arms 58 willresult in a constraining or restraining action on the sucker rodproduced by the links 78 and 80 and this will cause the sucker rod 48 toeffect a rearward revolving motion. Such rearward revolving motion willproduce a twisting action and will effect an initial twisting of thefront edge of the envelope or sheet 300 as shown in FIG. 10.

It must be understood that when the cam roll 74 is in the highestposition, the shaft 68 has rotated clockwise, causing the clevices 64 toarrive at their most forward position. In this position a gap is createdbetween block 66 and gap of arm 58. The suckers are now in their mostforward position. As the cam roll is forced down by the cam 76, theclevices are rotated clockwise, pulling the arms 58 rearward until thegap closes.

The arms 58 and sucker rod are prevented from moving downward because ofthe resistance of the spring 86. Clearing this action. the sucker rodhas moved rearward while the suckers have remained in the originalposition except for having rotated 23 in a twisting motion. Then the gaphaving closed, the arms must move downward because of the continuingrotary action of the rod 68 and clevices 64.

The initial rotational motion of the sucker rod 48 will rotate or twistthe leading edge of the envelope 30a in such a fashion that the edgewill separate from the envelope 30b immediately above it in the stack,as shown in FIGS. 3 and 10. The envelope 30a remains otherwise in itsoriginal position without being pulled forward. As the sucker rod 48rotates and at the same time moves backward, the normal vacuum betweenthe envelopes 30a and 30b is broken and when the sucker rod has movedback about a quarter of an inch, the timing is such that the arms 58will then start the downward mol 2 tion of the sucker rod 48, as shownin FIGS. 4 and 11.

As the sucker rod 48 moves downwardly to the position of FIG. 4, theslide plate 78 has moved forwardly to the extent that the roller 106 isnow free to roll up the edge 154 so as to enable the pressure roll 94,under the spring action 86A, to start moving toward the feed roll 100,as shown in FIG. 4.

The extreme forward movement of the slide plate 78 will permit thepressure roll 94 to move to its final position, as shown in FIG. 5,wherein it will hold the envelope 30a against the feed roll I00. Thefeed roll will frictionally move the envelope 30a forwardly to the nipbetween the pullout rolls I04 and the pulllout rolls will grasp thesheet and feed it onto the pullout 24 and to the printing presscylinders.

With regard to the slide plate 78 in its action on the roller 74 of thesucker rod assembly, it is sometimes desirable to delay the rise of thesuckers 50. This may be desirable in the instance of feeding longenvelopes or long sheets of types of stock. To effect such delay a slidearm 158 is disposed on the outer face of the slide 78 and is mounted byslots 16] on pins 160 for horizontal sliding movement. The arm has afront free end with a vertical cam edge 162 that is disposed in advanceof the cam segment 76, as shown clearly in FIG. 8. A catch I64 ispivoted on a pin 166 above the arm 158 and the catch and the arm haveinterlocking hook ends 168 and 170. A spring 172 is connected betweenthe arm and the catch and serves to urge the hook ends into interlockingengagement, as shown in FIG. 8.

When the slide plate starts its forward movement, the cam edge 162 ofthe arm will first engage the roller 74 but this will not result in adownward movement of the roller because the arm 158 will slide rearwardwith the spring 172 giving way to the crank lever 70 and permitting theends 168 and to break away and thus elongate the arm. In this respect,the arm 158 will slide rearwardly since the pins 160 are mounted in theslots in the arm, as shown in FIG. 8. Thus, the arm can slide rearwardlyto the position shown in FIG. 1 with the catch and the arm in the openposition. When the slide plate has moved to its rearward position, thespring 162 will be active to cause the two parts to be interlockedagain, as shown in FIG. 6.

A locking lever 176 is pivoted as at 178 and is adapted to swing downand to engage the spring retaining pin 174 on the arm for the purpose ofholding the arm in an open position, as shown in FIG I. When held insuch position, the catch and the arm will be in a spread apart position,as shown in FIG. 1 and the arm will be inactive. Thus, such mechanismcan be rendered inactive when running short envelopes or similar shortstock.

In FIG. 1 of the drawings, the cam or slide plate 78 has moved rearwardto nearly its maximum, with the slide arm 158 in its most forwardposition. With the slide arm in this position, the raise of the suckershas been delayed so the longer sheet may clear before the suckers raise.Now as the cam plate 78 moves rearward to its extreme position, theroller 74 raises slightly higher and therefore raises the arm anddisengages the lock as shown in FIG. 2. In this position the suckershave raised to their highest level.

Now as the cam plate 78 moves forward, the roller 74 contacts the armI58, holding it in this position as the cam plate moves. The bevel ofthe cam on the cam plate contacts the roller, forcing it downward andtherefore lowering the sucker bar. When the roller 74 has reached itslowest point and having forced the arm 158 rearward, as shown in FIG. 1,the slide then moves forward by the spring action to again lock inposition with the catch 164. The arm 158 can move forward as its lowersurface is slightly higher than the surface of the slide or cam plate74.

While the preferred embodiment of the present invention has beenillustrated in the accompanying drawings and described herein, it can beappreciated that other means can be provided for effecting the movementof the sucker rod and for realizing the coordinated movements of thesucker rod and the pressure roll.

In this respect, while the invention has been described and illustratedin connection with feeding envelopes to an offset printing press, it isobvious that this is merely one environment for the feeder. For thefeeder can be utilized in other environments where sheet material is fedto a sheet handling machine, regardless of the nature of the material orthe type and nature of the machine or mechanism.

Thus, the foregoing description and the accomapanying drawings aremerely exemplary of one form of and one environment for the presentinvention which is only limited by the scope and spirit of the appendedclaims.

What is claimed is:

l. A feeder for flexible sheet material comprising: a hopper means forreceiving and supporting a plurality of flexible sheets in a stack; avacuum gripping means movably disposed under said stack and adapted toengage a marginal edge portion of the lowermost sheet in the stack;means for initially moving said gripping means in a twisting motionwhile it is engaged with the lowermost sheet so as to twist the engagedsheet off of the stack and thereby separate such sheet from the nextuppermost sheet in the stack and consequently break the vacuum betweensuch sheets; means after cessation of the operation of the foregoingmeans and consequent completion of the twisting action for moving saidgripping means downwardly away from the stack with the sheet heldthereby and thus lowering the sheet from the stack; means for engagingthe edge portion of the next lowermost sheet in the stack and thusassisting in the separation of the sheets and also retaining the stackproperly within the hopper means as the engaged sheet is lowered fromthe stack; a conveying means to which the sheet is delivered by thegripping means for conveying the sheet from the feeder; means forreturning the gripping means upwardly back into engagement with the nextlowermost sheet in the stack, said gripping means including a sucker rodconstituting a manifold and having a plurality of suction cup sconstituting suckers mounted therein in communication therewith; meansconnecting the sucker rod to a vacuum source; said means for moving thegripping means downwardly from the stack including a pair of armsmounted for vertical swinging movement, and a rod supporting andactuating said arms and said sucker rod being carried by the arms, saidsucker rod being rotatably journaled in the arms and said means forinitially moving the gripping means in a twisting motion including aconstraining linkage connected to the sucker rod and to a fixed point soas to cause the sucker rod to rotate counterclockwise as the arms firstattempt to move it down away from the stack and spring means connectedto said arms to prevent the sucker rod from lowering until the twistingaction is completed and constituting the means for returning thegripping means to its raised position with the suction cups engaging thenext lower most sheet in the stack.

2. A feeder for flexible sheet material comprising; a hopper means forreceiving and supporting a plurality of flexible sheets in a stack; avacuum gripping means movably disposed under said stack and adapted toengage a marginal edge portion of the lowermost sheet in the stack;means for initially moving said gripping means in a twisting motionwhile it is engaged with the lowermost sheet so as to twist the engagedsheet off of the stack and thereby separate such sheet from the nextuppermost sheet in the stack and consequently break the vacuum betweensuch sheets; means after cessation of the operation of the foregoingmeans and consequent completion of the twisting action for moving saidgripping means downwardly away from the stack with the sheet heldthereby and thus lowering the sheet from the stack; means for engagingthe edge portion of the next lowermost sheet in the stack and thusassisting in the separation of the sheets and also retaining the stackproperly within the hopper means as the engaged sheet is lowered fromthe stack; a conveying means to which the sheet is delivered by thegripping means for conveying the sheet from the feeder; means forreturning the gripping means upwardly back into engagement with the nextlowermost sheet in the stack, said gripping means including a sucker rodconstituting a manifold and having a plurality of suction cupsconstituting suck ers mounted therein in communication therewith; meansconnecting the sucker rod to a vacuum source; said means for moving thegripping means downwardly from the stack including a pair of armsmounted for vertical swinging movement and a rod supporting andactuating said arms and said sucker rod being carried by the arms andincluding means engaging the supporting rod for the arms of the grippingmeans for adjusting the effective height of the gripping means relativeto the stack.

3. For use with a printing press having a vacuum means and having a feedlinkage, a feeder for feeding stock to the press comprising; hoppermeans for supporting the stock in a stack; vacuum gripping means movablydisposed under said stack and having means connecting it to the sourceof vacuum on the printing press with said gripping means being adaptedto engage a marginal edge portion of the lowermost sheet of stock in thestock; means actuated by the printing press feed linkage for moving saidgripping means downwardly away from the stack with the gripping meansgeing in communication with the vacuum means on the press and with thesheet held thereby so as to lower the sheet from the stack; meansresponsive to said foregoing moving means for initially twisting saidgripping means in a revolving motion while it is engaged with thelowermost sheet so as to twist the engaged sheet off of the stack andthereby separate such sheet from the next uppermost sheet in the stackand consequently break the vacuum between such sheets prior to thedownward movement of said gripping means which downward movement isinitiated and carried out only upon completion of the initial twistingaction; a conveying means to which the sheet is delivered by thegripping means for conveying the sheet from the feeder to the printingpress, said conveying means being actuated by the printing press intimed relation with the operation of the press; means for moving thegripping means upwardly back into engagement with the next lowermostsheet in the stack after the removed sheet is delivered to the conveyingmeans; said conveying means including a feed roll driven by the pressand onto which the sheet is lowered by the gripping means and a pressureroll adapted to clampingly hold the sheet against the feed roll andmeans for moving said pressure roll into and out of clamping relationwith the feed roll in timed relation with the movement of the grippingmeans; said last means including a rotatable rod, means connecting thepressure roll to said rod in spaced parallel and adjustable relationtherewith. means actuated by the press linkage for rotating the rod inone direction to hold the pressure roll out of engagement with the feedroll and spring means connected between a fixed point and the rotatablerod and operative upon the deactivation of said foregoing means to swingthe pressure roll into clamping relation with the feed roll.

4. The invention of claim 3 wherein said means for moving said grippingmeans downwardly away from the stack includes a rotating rod having abell crank, a reciprocating cam means driven by the press feed linkageand adapted to engage the crank for rotating the rod, a pair of armscarried by the rod and on which the gripping means is mounted, saidgripping means including a sucker rod having a plurality of suckers,said sucker rod being rotatably journaled in the arms and said means forinitially moving said gripping means in a twisting motion including arestraining linkage pivotally connected between the rod and a fixedpoint, said link age reacting to the downward movement of the arms toeffect an initial twisting motion of the sucker rod.

5. The invention of claim 4 including means engaging the rod carryingthe arms for the sucker rod for raising and lowering the effectiveheight of the sucker rod in relation to the stack.

6. The invention of claim 4 wherein said reciprocating cam means isprovided with means for delaying the rise of the sucker rod which meansmay be selectively employed in the instance of feeding longer sheets soas to permit such sheets to be clear of the conveying means before thespring means returns the sucker rod to its raised position.

7. The invention of claim 3 wherein a reciprocating cam means is drivenby the press feed linkage, said conveying means including a feed roll onwhich the removed sheet is placed by the gripping means, a pressureroll, means mounting the pressure roll for bodily movement relative tothe feed roll, means connecting the pressure roll to the cam means so itcan be held thereby out of engagement with the feed roll and springmeans connected between a fixed point and the mounting means for thepressure roll for moving it into en gagement of the feed roll after theremoved sheet has been delivered thereto by the gripping means, a rotat'able rod having a bell crank engaged by the cam means so as to rotatethe rod, a pair of arms carried by the rod and supporting the grippingmeans, said arms being swung downwardly by the cam means to move thegripping means downwardly and said twisting means including restrainingmeans pivotally connected between the gripping means and a fixed pointand reacting to the initial downward movement of the arms to effect theinitial twisting action of the gripping means and said means for movingthe gripping means upwardly back into engagement with the stackincluding springs connected between the arms and a fixed point, saidsprings also functioning to prevent the gripping means from loweringuntil the twisting motion is concluded.

8. A feeder for flexible sheet material comprising; a hopper means forreceiving and supporting a plurality of flexible sheets in a stack; avacuum gripping means movably disposed under said stack and adapted toengage a marginal edge portion of the lowermost sheet in the stack;means for initially moving said gripping means in a twisting motionwhile it is engaged with the lowermost sheet so as to twist the engagedsheet off of the stack and thereby separate such sheet from the nextuppermost sheet in the stack and consequently break the vacuum betweensuch sheets; means after cessation of the operation of the foregoingmeans and consequent completion of the twisting action for moving saidgripping means downwardly away from the stack with the sheet heldthereby and thus lowering the sheet from the stack; means for engagingthe edge portion of the next lowermost sheet in the stack and thusassisting in the separation of the sheets and also retaining the stackproperly within the hopper means as the engaged sheet is lowered fromthe stack; a conveying means to which the sheet is delivered by thegripping means for conveying the sheet from the feeder; means forreturning the gripping means upwardly back into engagement with the nextlowermost sheet in the stack; said conveying means including a rotatingfeeed roll on which the sheet is deposited by the gripping means, apressure roll operable to clamp the sheet against the feed roll, a pairof rotating pull-out rolls into the nip of which the sheet is fed by thefeed roll, means operating in consort and timed relation with the meansfor moving the gripping means for moving the pressure roll into and outof sheet clamping relation with the feed roll, said last means includingspring means connected to the pressure roll for swinging the pressureroll into sheet clamping relation with the feed roll, said means formoving the gripping means downwardly including a cam slide mechanismdriven in a rectilinearly reciprocating path, said pressure roll havinga crank means, a roller carried by the crank means and engaged by thecam slide mechanism to hold the pressure roll away from the feed roll inopposition to the action of the spring means until the gripping meanshas been moved to its lowermost position with the removed sheet, saidrod for the arms of the gripping means having the arms pivotallyconnected thereto and said rod having a crank end, a roller on the crankend engaged by the cam slide mechanism which swings the arms downwardlywhile maintaining the pressure roll in its position out of contact withthe feed roll until the gripping means delivers the removed sheet to thefeed roll.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No.3,893,664 Dated July 1975 Inv nto ELMER R. THOMSEN It is certified thaterror appears in the above-identified patent and that said LettersPatent are hereby corrected as shown below:

Claim 3, line 51, change "stock" to stack-;

line 52, change "geing" to -being-.

Claim 8, line 35, change "feeed" to -feed.

Signed and Scaled this sixteenth Day Of September1975 [SEAL] Arrest:

RUTH C. MASON C. MARSHALL DANN Arresting Officer (nmmlssivm'r ufParenrsand Trademarks

1. A feeder for flexible sheet material comprising: a hopper means forreceiving and supporting a plurality of flexible sheets in a stack; avacuum gripping means movably disposed under said stack and adapted toengage a marginal edge portion of the lowermost sheet in the stack;means for initially moving said gripping means in a twisting motionwhile it is engaged with the lowermost sheet so as to twist the engagedsheet off of the stack and thereby separate such sheet from the nextuppermost sheet in the stack and consequently break the vacuum betweensuch sheets; means after cessation of the operation of the foregoingmeans and consequent completion of the twisting action for moving saidgripping means downwardly away from the stack with the sheet heldthereby and thus lowering the sheet from the stack; means for engagingthe edge portion of the next lowermost sheet in the stack and thusassisting in the separation of the sheets and also retaining the stackproperly within the hopper means as the engaged sheet is lowered fromthe stack; a conveying means to which the sheet is delivered by thegripping means for conveying the sheet from the feeder; means forreturning the gripping means upwardly back into engagement with the nextlowermost sheet in the stack, said gripping means including a sucker rodconstituting a manifold and having a plurality of suction cupsconstituting suckers mounted therein in communication therewith; meansconnecting the sucker rod to a vacuum source; said means for moving thegripping means downwardly from the stack including a pair of armsmounted for vertical swinging movement, and a rod supporting andactuating said arms and said sucker rod being carried by the arms, saidsucker rod being rotatably journaled in the arms and said means forinitially moving the gripping means in a twisting motion including aconstraining linkage connected to the sucker rod and to a fixed point soas to cause the sucker rod to rotate counterclockwise as the arms firstattempt to move it down away from the stack and spring means connectedto said arms to prevent the sucker rod from lowering until the twistingaction is completed and constituting the means for returning thegripping means to its raised position with the suction cups engaging thenext lower most sheet in the stack.
 2. A feeder for flexible sheetmaterial comprising; a hopper means for receiving and supporting aplurality of flexible sheets in a stack; a vacuum gripping means movablydisposed under said stack and adapted to engage a marginal edge portionof the lowermost sheet in the stack; means for initially moving saidgripping means in a twisting motion while it is engaged with thelowermost sheet so as to twist the engaged sheet off of the stack andthereby separate such sheet from the next uppermost sheet in the stackand consequently break the vacuum between such sheets; means aftercessation of the operation of the foregoing means and consequentcompletion of the twisting action for moving said gripping meansdownwardly away from the stack with the sheet held thereby and thuslowering the sheet from the stack; means for engaging the edge portionof the next lowermost sheet in the stack and thus assisting in theseparation of the sheets and also retaining the stack properly withinthe hopper means as the enGaged sheet is lowered from the stack; aconveying means to which the sheet is delivered by the gripping meansfor conveying the sheet from the feeder; means for returning thegripping means upwardly back into engagement with the next lowermostsheet in the stack, said gripping means including a sucker rodconstituting a manifold and having a plurality of suction cupsconstituting suckers mounted therein in communication therewith; meansconnecting the sucker rod to a vacuum source; said means for moving thegripping means downwardly from the stack including a pair of armsmounted for vertical swinging movement and a rod supporting andactuating said arms and said sucker rod being carried by the arms andincluding means engaging the supporting rod for the arms of the grippingmeans for adjusting the effective height of the gripping means relativeto the stack.
 3. For use with a printing press having a vacuum means andhaving a feed linkage, a feeder for feeding stock to the presscomprising; hopper means for supporting the stock in a stack; vacuumgripping means movably disposed under said stack and having meansconnecting it to the source of vacuum on the printing press with saidgripping means being adapted to engage a marginal edge portion of thelowermost sheet of stock in the stock; means actuated by the printingpress feed linkage for moving said gripping means downwardly away fromthe stack with the gripping means geing in communication with the vacuummeans on the press and with the sheet held thereby so as to lower thesheet from the stack; means responsive to said foregoing moving meansfor initially twisting said gripping means in a revolving motion whileit is engaged with the lowermost sheet so as to twist the engaged sheetoff of the stack and thereby separate such sheet from the next uppermostsheet in the stack and consequently break the vacuum between such sheetsprior to the downward movement of said gripping means which downwardmovement is initiated and carried out only upon completion of theinitial twisting action; a conveying means to which the sheet isdelivered by the gripping means for conveying the sheet from the feederto the printing press, said conveying means being actuated by theprinting press in timed relation with the operation of the press; meansfor moving the gripping means upwardly back into engagement with thenext lowermost sheet in the stack after the removed sheet is deliveredto the conveying means; said conveying means including a feed rolldriven by the press and onto which the sheet is lowered by the grippingmeans and a pressure roll adapted to clampingly hold the sheet againstthe feed roll and means for moving said pressure roll into and out ofclamping relation with the feed roll in timed relation with the movementof the gripping means; said last means including a rotatable rod, meansconnecting the pressure roll to said rod in spaced parallel andadjustable relation therewith, means actuated by the press linkage forrotating the rod in one direction to hold the pressure roll out ofengagement with the feed roll and spring means connected between a fixedpoint and the rotatable rod and operative upon the deactivation of saidforegoing means to swing the pressure roll into clamping relation withthe feed roll.
 4. The invention of claim 3 wherein said means for movingsaid gripping means downwardly away from the stack includes a rotatingrod having a bell crank, a reciprocating cam means driven by the pressfeed linkage and adapted to engage the crank for rotating the rod, apair of arms carried by the rod and on which the gripping means ismounted, said gripping means including a sucker rod having a pluralityof suckers, said sucker rod being rotatably journaled in the arms andsaid means for initially moving said gripping means in a twisting motionincluding a restraining linkage pivotally connected between the rod anda fixed point, said linkage reacting to the downward movement of thearms to effect an initiaL twisting motion of the sucker rod.
 5. Theinvention of claim 4 including means engaging the rod carrying the armsfor the sucker rod for raising and lowering the effective height of thesucker rod in relation to the stack.
 6. The invention of claim 4 whereinsaid reciprocating cam means is provided with means for delaying therise of the sucker rod which means may be selectively employed in theinstance of feeding longer sheets so as to permit such sheets to beclear of the conveying means before the spring means returns the suckerrod to its raised position.
 7. The invention of claim 3 wherein areciprocating cam means is driven by the press feed linkage, saidconveying means including a feed roll on which the removed sheet isplaced by the gripping means, a pressure roll, means mounting thepressure roll for bodily movement relative to the feed roll, meansconnecting the pressure roll to the cam means so it can be held therebyout of engagement with the feed roll and spring means connected betweena fixed point and the mounting means for the pressure roll for moving itinto engagement of the feed roll after the removed sheet has beendelivered thereto by the gripping means, a rotatable rod having a bellcrank engaged by the cam means so as to rotate the rod, a pair of armscarried by the rod and supporting the gripping means, said arms beingswung downwardly by the cam means to move the gripping means downwardlyand said twisting means including restraining means pivotally connectedbetween the gripping means and a fixed point and reacting to the initialdownward movement of the arms to effect the initial twisting action ofthe gripping means and said means for moving the gripping means upwardlyback into engagement with the stack including springs connected betweenthe arms and a fixed point, said springs also functioning to prevent thegripping means from lowering until the twisting motion is concluded. 8.A feeder for flexible sheet material comprising; a hopper means forreceiving and supporting a plurality of flexible sheets in a stack; avacuum gripping means movably disposed under said stack and adapted toengage a marginal edge portion of the lowermost sheet in the stack;means for initially moving said gripping means in a twisting motionwhile it is engaged with the lowermost sheet so as to twist the engagedsheet off of the stack and thereby separate such sheet from the nextuppermost sheet in the stack and consequently break the vacuum betweensuch sheets; means after cessation of the operation of the foregoingmeans and consequent completion of the twisting action for moving saidgripping means downwardly away from the stack with the sheet heldthereby and thus lowering the sheet from the stack; means for engagingthe edge portion of the next lowermost sheet in the stack and thusassisting in the separation of the sheets and also retaining the stackproperly within the hopper means as the engaged sheet is lowered fromthe stack; a conveying means to which the sheet is delivered by thegripping means for conveying the sheet from the feeder; means forreturning the gripping means upwardly back into engagement with the nextlowermost sheet in the stack; said conveying means including a rotatingfeeed roll on which the sheet is deposited by the gripping means, apressure roll operable to clamp the sheet against the feed roll, a pairof rotating pull-out rolls into the nip of which the sheet is fed by thefeed roll, means operating in consort and timed relation with the meansfor moving the gripping means for moving the pressure roll into and outof sheet clamping relation with the feed roll, said last means includingspring means connected to the pressure roll for swinging the pressureroll into sheet clamping relation with the feed roll, said means formoving the gripping means downwardly including a cam slide mechanismdriven in a rectilinearly reciprocating path, said pressure roll havinga crank means, a roller carried by the crank mEans and engaged by thecam slide mechanism to hold the pressure roll away from the feed roll inopposition to the action of the spring means until the gripping meanshas been moved to its lowermost position with the removed sheet, saidrod for the arms of the gripping means having the arms pivotallyconnected thereto and said rod having a crank end, a roller on the crankend engaged by the cam slide mechanism which swings the arms downwardlywhile maintaining the pressure roll in its position out of contact withthe feed roll until the gripping means delivers the removed sheet to thefeed roll.